“Learn about the biochemical impacts of vitamin deficiencies on amino acid metabolism and how these impairments affect your health. Dive into detailed explanations and pathways now!”
“Vitamin deficiencies and impaired amino acid metabolism table”
| Vitamin | Impaired Reaction | Enzyme Affected | Reaction Catalyzed | Pathway/Consequence |
| Vitamin B6 (PLP) | Transamination of amino acids | Aminotransferases (e.g., ALT, AST) | Alanine + α-Ketoglutarate ↔ Pyruvate + Glutamate | Impaired amino acid catabolism and gluconeogenesis |
| Conversion of glutamate to γ-aminobutyric acid (GABA) | Glutamate decarboxylase | Glutamate → GABA + CO₂ | Impaired neurotransmitter synthesis | |
| Conversion of homocysteine to cystathionine and cysteine | Cystathionine β-synthase | Homocysteine + Serine → Cystathionine | Homocysteine accumulation | |
| Thiamine (B1) | Oxidative decarboxylation of branched-chain α-keto acids | Branched-chain α-keto acid dehydrogenase | Valine, Leucine, Isoleucine α-keto acids + NAD⁺ → Acyl-CoA + NADH + CO₂ | Impaired branched-chain amino acid catabolism |
| Folate (B9) | Conversion of homocysteine to methionine (methyl group transfer) | Methionine synthase (with Vitamin B12) | Homocysteine + 5-Methyl-THF → Methionine + THF | Homocysteine accumulation, disrupted methylation |
| Vitamin B12 | Conversion of methylmalonyl-CoA to succinyl-CoA | Methylmalonyl-CoA mutase | Methylmalonyl-CoA → Succinyl-CoA | Impaired odd-chain fatty acid and amino acid metabolism |
| Conversion of homocysteine to methionine | Methionine synthase | Homocysteine + 5-Methyl-THF → Methionine + THF | Homocysteine accumulation, impaired SAM synthesis | |
| Riboflavin (B2) | Oxidation of L-amino acids (e.g., proline, lysine) | L-amino acid oxidase | L-Amino acid + FAD → α-Imino acid + FADH₂ | Impaired amino acid degradation |
| Biotin | Carboxylation in amino acid metabolism | Propionyl-CoA carboxylase | Propionyl-CoA + CO₂ + ATP → Methylmalonyl-CoA + ADP + Pi | Impaired catabolism of valine, isoleucine, threonine |
Key Reactions Explained:
- Vitamin B6 (PLP):
- Aminotransferases (ALT, AST): Vital for interconversion of amino acids and keto acids in transamination reactions.
- Cystathionine β-synthase: Converts homocysteine and serine to cystathionine, and then to cysteine, preventing homocysteine buildup.
- Glutamate decarboxylase: Critical for GABA synthesis, affecting neurotransmission.
- Thiamine (B1):
- Branched-chain α-keto acid dehydrogenase: Catalyzes oxidative decarboxylation in branched-chain amino acid catabolism (e.g., valine, leucine).
- Folate (B9) and Vitamin B12:
- Methionine synthase: Facilitates methylation cycles by regenerating methionine from homocysteine.
- Biotin:
- Propionyl-CoA carboxylase: Handles catabolism of amino acids generating propionyl-CoA (e.g., valine, isoleucine).
